"Zahra and Maryam have been best friends since childhood in Karachi, even though--or maybe because--they are unlike in nearly every way. Yet they never speak of the differences in their backgrounds or their values, not even after the fateful night when a moment of adolescent impulse upends their plans for the future. Three decades later, Zahra and Maryam have grown into powerful women who have each cut a distinctive path through London. But when two...